The Sinn Féin president steps down next weekend after 50 years in politics when a special ard fheis ratifies his successor, Mary Lou McDonald.

Speaking during an interview with the BBC’s Andrew Marr, Mr Adams said after decades of conflict people had got used to peace, adding: “The images...of border checkpoints, heavy patrols ... that all belongs to history and nobody wants that back.

My position has been consistent that I was not a member of the IRA but I’ve never distanced myself from the IRA

“Brexit is disastrous for the people of Ireland. The British government are not at all clear about what their future relationship with the European Union is going to be and they are arguing that they are going to leave the customs union and they are going to leave the single market and that will end up a complete disaster for people here on the island of Ireland,” Mr Adams said.

Gerry Adams: I was not a member of the IRA but I’ve never distanced myself from the IRA

He said the agreement that moved the negotiations between the British government and the European Union on Britain’s plan to leave the EU, to a second phase “was a fudge, it’s filled with contradictions”.

“The solution to this problem is special designated status for the North within the European Union,” Mr Adams said. He added that that was “very, very doable”

In a wide-ranging 11-minute, sit-down interview for BBC One’s The Andrew Marr show, Mr Adams was asked why he had not joined the IRA, having repeatedly denied he was a member. “Because I was active in Sinn Féin when the IRA was non-existent in the 1960s,” he told Marr.

“I would like to see Jeremy in that position for the benefit of people in Britain, leaving Ireland out of it.

“I think Jeremy is an outstanding politician and I hope my endorsement of him is not used against him in the time ahead.”

He and (former London Mayor) Ken Livingstone and others kept faith and they were the people who said, when others said no, talk. “They were the people who were open to conversation about how to deal with conflict and how to get conflict resolution processes.”

Mr Corbyn, Britain’s Labour Party leader, and shadow chancellor John McDonnell have faced scrutiny over their association with the republicans.

Before the IRA ceasefire, they controversially met Sinn Féin a number of times in Westminster during the 1990s.

Mr Adams said former British prime minister Tony Blair enjoyed an “opportunity on a plate” for peace in Ireland and that he had seized it leading to the Belfast Agreement in 1998 that ended decades of violence. Mr Adams said he told Mr Blair not to invade Iraq in 2003. “We said to him, look at the Irish experience, don’t go in there.”

He said nobody could stand over the killing of children or civilians during the IRA’s campaign. The outgoing political leader, who for decades defended republican violence but was instrumental in its cessation, reflected on the “awfulness and horror of war”.

He said: “I would wish that no one had been killed or injured in the course of the conflict.

“We were able to come to an alternative. When you come forward with an alternative sensible people will embrace that alternative.”